In semiconductor manufacture for automatic wafer-level testing, a tester is used to transmit testing signals to a device under test (DUT), e.g. an integrated circuit (IC), and to read the testing result from the DUT. However, since the pin pitch of the DUT is relatively small to that of the tester, a probe system is required to be disposed between the DUT and the tester for space transforming. In this way, the testing signals from the tester can be transmitted to the testing pads of the DUT through the circuit and probes of the probe system, and the testing result from the DUT can be transmitted back to the tester through the probes and the circuit of the probe system for the tester to determine if the DUT has failed or not.
For those DUTs of high-speed/high-frequency operation or DUTs having high-frequency/low-frequency mixed operations, the layout on the circuit substrate for the circuit of the probe system has to be designed specifically in order to meet the requirement of impedance matching on the transmission paths for the high-frequency signals because the high-frequency signals are highly sensitive to the transmission environment. If the impedance of each component in the probe system does not exactly match to one another, signal reflection loss at the conjunctions between each component then occurs, which thereby deteriorates the reliability of the probe system.
However, for the sake of mass production, the probe system manufacturer applies standard circuit substrates to fabricate circuits of all types of probe systems. Since testing contacts on such standard circuit substrate are fixed, hand wires, acting as signal transmission paths between the tester and the probes, are required for the standard circuit substrate to be able to apply to different kinds of probe systems. Consequently, such design cannot meet the impedance requirement for high-frequency transmission and therefore is only adapted to low-frequency/medium-frequency transmissions. That is, the probe system manufacturer can utilize the standard circuit substrate for DUTs of low-frequency/medium-frequency operations, but the probe system manufacturer has to use another customized circuit substrate for DUTs of high-frequency operations or low-frequency/medium-frequency/high-frequency mixed operations since the high-frequency transmission requires impedance matching on the signal transmission paths. Even if the probe system manufacturer utilizes a customized circuit substrate for the probe system to test DUTs of same frequency requirements, the probe system manufacturer still has to re-design the customized circuit substrate whenever the layouts of the DUTs are changed, which thereby increases the overall costs.
Taiwan patent publication No. 1266882 discloses a probe system for providing signal paths between the tester and the DUT. The probe system disposes an additional area on the circuit substrate, and this additional area is only for receiving the high-frequency signals through the additional flex cables. In other words, the circuit substrate of the probe system is divided into two areas: one area is for low-frequency signals/medium-frequency signals, and the other area is only for high-frequency signals. Consequently, the tester has to separate the positions for the low-frequency testing signals/medium-frequency testing signals and the positions for the high-frequency testing signals into two different areas, which affects the layout for low-frequency/medium-frequency transmission on the circuit substrate and diminishes the amount of circuit space required by the high-frequency transmission paths. Meanwhile, the extending of the flex cables from the circuit substrate into the high-density probe area directly generates resistance to the resilience of the probes, especially for those probe structures requiring specific resilience, which causes the resilient force/reaction force between one testing pad of the DUT and its corresponding probe to be different from the resilient force/reaction force between another testing pad of the DUT and its corresponding probe. Under such usage condition, after a period of time, resilience of all probes will be different to each other, which deteriorates the electrical connections between the probe system and the DUT and thereby decreases the testing reliability. Furthermore, if the DUT has more components having different high-frequency requirements, the above probe system needs to install more flex cables at different places of the circuit substrate for transmitting those high-frequency signals to those components of the DUT so that more flex cables are inserted into the high-density probe area, and more resistance to the probes is generated. Besides, if any flex cable is moved, for example, as when touched by the operator, all probes will be misplaced or even damaged, and then the testing procedure has to be stopped until the probe system is completely repaired.
Therefore, it is quite a problem for the probe system manufacturer to provide the probe system having the higher transmission quality for low-frequency/medium-frequency/high-frequency testing signals with the shortest lead time and the lower cost.